Sensor cleaning system, sensor cleaning method, and vehicle

1. A sensor cleaning system that cleans a sensor surface of an external sensor mounted on a vehicle, the sensor cleaning system comprising one or more processors, wherein the one or more processors:

estimate a water droplet amount of a water droplet adhering to the sensor surface;

determine whether a cleaning start condition is satisfied based on the water droplet amount; and

execute a cleaning process, including controlling a pump to supply a cleaning liquid to the sensor surface, of cleaning the sensor surface with the supplied cleaning liquid when the cleaning start condition based on the water droplet amount is satisfied, the cleaning start condition includes a first period in which the water droplet does not dry and the first period is defined by a first time point and a second time point, and a second period in which drying of the water droplet progresses and the second period is defined by the second time point and a third time point, and the cleaning process is executed between the second time point and the third time point.

2. The sensor cleaning system according to claim 1 , wherein the cleaning start condition includes that the water droplet amount is currently decreasing after the water droplet amount increases.

3. The sensor cleaning system according to claim 2 , wherein the cleaning start condition includes that the water droplet amount changes from an increase to a decrease.

4. The sensor cleaning system according to claim 2 , wherein the cleaning start condition includes that the water droplet amount exceeds a first threshold value and then changes from an increase to a decrease.

5. The sensor cleaning system according to claim 2 , wherein the cleaning start condition includes that the water droplet amount exceeds a second threshold value and then falls below a third threshold value.

6. The sensor cleaning system according to claim 1 , wherein the cleaning start condition includes that a certain period of time elapses after the water droplet amount exceeds a fourth threshold value.

7. The sensor cleaning system according to claim 1 , wherein the one or more processors estimate the water droplet amount of the water droplet adhering to the sensor surface based on a measurement result by the external sensor.

8. A sensor cleaning method for cleaning a sensor surface of an external sensor mounted on a vehicle with a cleaning liquid, the method comprising:

an estimation process of estimating a water droplet amount of a water droplet adhering to the sensor surface;

a determination process of determining whether a cleaning start condition is satisfied based on the water droplet amount; and

a cleaning process, including controlling a pump to supply a cleaning liquid to the sensor surface, of cleaning the sensor surface with the supplied cleaning liquid when the cleaning start condition based on the water droplet amount is satisfied, the cleaning start condition includes a first period in which the water droplet does not dry and the first period is defined by a first time point and a second time point, and a second period in which drying of the water droplet progresses and the second period is defined by the second time point and a third time point, and the cleaning process is executed between the second time point and the third time point.

9. A vehicle comprising:

an external sensor; and

a sensor cleaning system that cleans a sensor surface of the external sensor with a cleaning liquid, wherein the sensor cleaning system;

estimates a water droplet amount of a water droplet adhering to the sensor surface,

determines whether a cleaning start condition is satisfied based on the water droplet amount, and

executes a cleaning process, including controlling a pump to supply a cleaning liquid to the sensor surface, of cleaning the sensor surface with the supplied cleaning liquid when the cleaning start condition based on the water droplet amount is satisfied, the cleaning start condition includes a first period in which the water droplet does not dry and the first period is defined by a first time point and a second time point, and a second period in which drying of the water droplet progresses and the second period is defined by the second time point and a third time point, and the cleaning process is executed between the second time point and the third time point.